[SIMPL-30451] Correct stale references in the guide and verify both images build

The rename of process_work_units and _results_from_pipes during the fan-out refactor left three references behind, in the guide, the checklist and the loosely coupled module docstring. The guide also showed loosely_coupled_k8s_job without its executor_def and claimed the pipes client replaced the executor, which stopped being true once the graph fanned out.

Both images were built and smoke tested: the code location image loads its definitions, and the payload image ships dagster_pipes without dagster. That check is now recorded as L11 in the readiness checklist, so the isolation argument is verified at image level and not only in the source.

Changelog: fixed

README.md

@@ -77,6 +77,10 @@ docker build -t distributed-execution:0.1.0 .
 docker build -f payload/Dockerfile -t distributed-execution-payload:0.1.0 payload/
 ```
 
+Both images build and have been smoke tested locally: the code location image
+loads its definitions, and the payload image contains `dagster_pipes` without
+`dagster` — check L11 in the readiness checklist.
+
 ## Status
 
 Both execution targets are implemented. The tightly coupled jobs and the loosely

documents/user-guide/distributed-execution-guide.md

@@ -312,16 +312,22 @@ def dispatch_external_work_k8s(
     return _result_from_pipes(context, completed)
 ```
 
-and the job supplies the client as a resource instead of an executor:
+and the job supplies the client as a resource:
 
 ```python
 loosely_coupled_k8s_job = loosely_coupled_k8s_reference.to_job(
     name="loosely_coupled_k8s_job",
+    executor_def=multiprocess_executor.configured({"max_concurrent": 2}),
     resource_defs={"pipes_k8s_client": PipesK8sClient()},
     tags={**COMMON_TAGS, "transport": "k8s_pod_logs"},
 )
 ```
 
+The executor is still present, but its meaning has changed. It no longer decides
+where the work runs — the payload image and `namespace` do that. It only bounds
+how many dispatching ops wait on the message channel at once. The two decisions
+that were fused in the tightly coupled setup are now independent.
+
 #### What changes operationally
 
 | | Tightly coupled | Loosely coupled |
@@ -366,7 +372,7 @@ distinct external workers, which is the loosely coupled equivalent of the
 reference uses. It needs no extra infrastructure, but it couples message
 delivery to the pod log stream — a log shipper that intercepts or truncates
 stdout will break reporting while the workload still exits 0. That is why
-`_results_from_pipes` raises on an empty message list rather than returning an
+`_result_from_pipes` raises on an empty message list rather than returning an
 empty result. If your cluster's logging setup makes that transport unreliable,
 switch to an object-storage message reader, which needs a bucket plus
 credentials on both sides.
@@ -462,7 +468,8 @@ Tracked under SIMPL-30451.
 | Before-and-after example, switching to loosely coupled | AC4 | Complete |
 | Runnable tightly coupled reference implementations | AC4 | Complete |
 | Runnable loosely coupled reference implementation | AC4 | Complete (subprocess verified, K8s not cluster-run) |
-| Payload image published to the registry | Tech details | **Pending** |
+| Both images build; payload image passes the isolation check (L11) | Tech details | Complete |
+| Payload image published to the container registry | Tech details | **Pending** — needs the CI build job |
 | End-to-end run of `loosely_coupled_k8s_job` on a cluster | Tech details | **Pending** |
 | Screenshots of UI surfaces | Tech details | **Pending** |
 | Platform architecture document update | Tech details | **Pending** |

documents/user-guide/readiness-checklist.md

@@ -9,8 +9,9 @@ location image.
 
 > **NOT CLUSTER-VERIFIED.** Checks L4–L9 and the Kubernetes rows of section 4.3
 > are derived from the implemented reference but have not yet been run against a
-> Simpl cluster. Checks L1–L3 and L10, which exercise the payload contract, the
+> Simpl cluster. Checks L1–L3, L10 and L11, which exercise the payload contract,
-> message-parsing path and per-unit dispatch, are covered by the test suite.
+> the message-parsing path, per-unit dispatch and image-level isolation, are
+> verified locally.
 
 ---
 
@@ -52,9 +53,10 @@ location image.
 | L8 | Payload has **no** orchestration connectivity | Same run; inspect run logs | No `Payload could see orchestration runtime credentials` warning. This is a positive check — absence of errors is not sufficient |
 | L9 | Work ran off-platform | Same run | `summarise_results` metadata shows `contributing_hosts` containing the payload pod names, not the run worker's hostname |
 | L10 | One workload dispatched per unit | Same run, or `uv run pytest -k dispatched_to_its_own` locally | `contributing_workers` has one entry per unit; the local test asserts four distinct external workers |
+| L11 | Payload **image** carries no orchestration dependency | `docker run --rm <payload-image> python -c "import importlib.util; print(importlib.util.find_spec('dagster') is not None)"` | Prints `False`. L1 proves the *source* does not import `dagster`; this proves the shipped image does not contain it either |
 
-Checks L4–L9 require a cluster. L1–L3 and L10 run on a laptop and should gate
+Checks L4–L9 require a cluster. L1–L3, L10 and L11 run on a laptop and should
-every change to the payload or the dispatching op.
+gate every change to the payload or the dispatching op.
 
 ---
 
@@ -90,7 +92,7 @@ every change to the payload or the dispatching op.
 | Op hangs until `pod_wait_timeout` (default 24 h) | Payload Job never scheduled — quota, node selector or image pull | Check `kubectl -n <payload-ns> describe job <name>`; lower `pod_wait_timeout` so the failure surfaces quickly |
 | `403 Forbidden` creating the Job | Dispatcher service account lacks Job create permission | Apply `yaml/loosely-coupled/rbac-pipes-dispatch.yaml` in the **payload** namespace |
 | Warning: `Payload could see orchestration runtime credentials` | Payload pod inherited run-pod env or a Vault annotation | Remove the inherited env; the payload should receive only what `extras` and explicit `env` pass it |
-| Payload exits non-zero but the run reports success | Exit status not being checked, or messages read before failure | Confirm the dispatching op returns through `_results_from_pipes`; do not swallow `PipesClientCompletedInvocation` errors |
+| Payload exits non-zero but the run reports success | Exit status not being checked, or messages read before failure | Confirm the dispatching op returns through `_result_from_pipes`; do not swallow `PipesClientCompletedInvocation` errors |
 | Payload receives no `units` | `extras` key mismatch between dispatcher and `pipes.get_extra()` | Both sides must use the same key; a typo yields a `KeyError` inside the payload |
 | Run cancelled in the UI, payload pod keeps running | Cancellation is not propagated to dispatched workloads automatically | `delete_pod_on_completion` handles the normal path; for cancellation, verify orphaned Jobs and add a cleanup sensor |
 
@@ -108,8 +110,9 @@ change record:
 1. The run ID and its final status.
 2. The `report_execution_target` output metadata block (pod identity, namespace,
    env var presence).
-3. The `summarise_results` metadata block (`contributing_hosts`), which proves
+3. The `summarise_results` metadata block (`contributing_hosts` and
-   which execution target was actually used.
+   `contributing_workers`), which proves which execution target was actually
+   used and that the fan-out reached it.
 4. For `k8s_job_executor`, the output of `kubectl get jobs -l dagster/run-id=<run-id>`.
 5. For the loosely coupled target, the payload image digest and the run log line
    emitted by `pipes.log` — together they prove which payload version ran and

src/distributed_execution/loosely_coupled/jobs.py

@@ -6,7 +6,7 @@ dagster-pipes protocol, which Dagster materialises as logs and metadata. The
 payload never connects to the metadata database.
 
 Two transports are provided. Both dispatch the *same* payload script and produce
-the same output shape as the tightly coupled ``process_work_units`` op, so the
+the same output shape as the tightly coupled ``process_work_unit`` op, so the
 graphs differ by exactly one node - see the guide's section 5.3.
 """